Radio communication system and scheduling method

ABSTRACT

A radio communication system and scheduling method where, when data are transmitted from a plurality of transmit antennas to respective different mobile station apparatuses, all the mobile station apparatuses precisely receive data addressed thereto. A scheduler ( 104 ) performs scheduling that determines a data transmit order, depending on the numbers of receive antennas of the respective mobile station apparatuses, and notifies a transmit antennas assignment signal generator ( 124 ) of which transmit antenna is assigned which mobile station apparatus&#39;s sub-stream as the scheduling result. A number of receive antennas notifying signal decoder ( 122 ) decodes the number of receive antennas notifying signals and notifies the number of the receive antennas of each mobile station apparatus to the scheduler ( 104 ). The transmit antennas assignment signal generator ( 124 ) generates the transmit antennas assignment signal indicating which transmit antenna is assigned which mobile station apparatus&#39;s sub-stream.

TECHNICAL FIELD

The present invention relates to a radio communication system and ascheduling method.

BACKGROUND ART

In recent years, for HSDPA (High Speed Downlink Packet Access) whichtransmits packet data at high speed on a downlink, applying MIMO (MultiInput Multi Output) communication wherein a plurality of transmitantennas transmit respectively different packets of data simultaneouslyusing the same frequency and the same code has been examined in order tofurther increase transmission speed. When performing the MIMOcommunication, signals transmitted from the plurality of transmitantennas are received by a mobile station apparatus provided with thesame number of, or more, receive antennas as the transmit antennas ofthe base station apparatus, and a matrix operation is performed on thesignals received by the respective receive antennas to separate intopackets of data transmitted by the respective plurality of transmitantennas, which are then demodulated and decoded.

In HSDPA having the above MIMO communication applied thereto, whentransmitting packets of data to a plurality of mobile stationapparatuses, the base station apparatus may transmit packets of datafrom the plurality of transmit antennas respectively to the differentmobile station apparatuses simultaneously. For example, a base stationapparatus provided with two transmit antennas may assign one transmitantenna to a mobile station apparatus and the other transmit antenna toanother mobile station apparatus, and transmit packets of datasimultaneously.

In the case where a base station apparatus assigns a plurality oftransmit antennas respectively to different mobile station apparatusesand transmits packets of data simultaneously as described above, ifevery mobile station apparatus receiving the packets of data has thesame number of, or more, receive antennas as the transmit antennas ofthe base station apparatus, each mobile station apparatus can correctlyseparate the packets of data transmitted from the respective transmitantennas and demodulate and decode the packet of data addressed thereto.

However, if the number of receive antennas of a mobile station apparatusis less than the number of the transmit antennas of the base stationapparatus, the mobile station apparatus cannot correctly separate thepackets of data transmitted from the respective transmit antennas, sothat packets of data addressed to other apparatuses become aninterference component, thus causing the problem that receive qualitydegrades.

DISCLOSURE OF INVENTION

An object of the present invention is to enable all mobile stationapparatuses to precisely receive data addressed thereto when data aretransmitted from a plurality of transmit antennas to the respectivedifferent mobile station apparatuses.

The subject of the present invention is that each mobile stationapparatus notifies the number of receive antennas provided in the mobilestation apparatus to a base station apparatus, and the base stationapparatus performs scheduling such that all the mobile stationapparatuses correctly separate, on a per transmit antenna basis, datatransmitted via a plurality of transmit antennas, based on the notifiednumbers of the receive antennas of the mobile station apparatuses.

According to an embodiment of the present invention, a radiocommunication system that has a mobile station apparatus group of whichat least one mobile station apparatus is provided with a plurality ofreceive antennas and a base station apparatus that transmits data to themobile station apparatus group via a plurality of transmit antennas isconfigured that each mobile station apparatus of the mobile stationapparatus group comprises a number of receive antennas notifying signaltransmit section that transmits a number of receive antennas notifyingsignal indicating the number of receive antennas provided for the mobilestation apparatus, and that the base station apparatus comprises anumber of receive antennas notifying signal receive section thatreceives the number of receive antennas notifying signals; a transmitorder determining section that determines order in which data aretransmitted based on the number of receive antennas notifying signalsreceived; and a data transmit section that assigns the data to theplurality of transmit antennas according to the determined transmitorder and transmits.

According to another embodiment of the present invention, a base stationapparatus that transmits data via a plurality of transmit antennascomprises a number of receive antennas notifying signal receive sectionthat receives number of receive antennas notifying signals indicatingthe numbers of receive antennas provided for communication partnerstations; a transmit order determining section that determines order inwhich data are transmitted based on the number of receive antennasnotifying signals received; and a data transmit section that assigns thedata to the plurality of transmit antennas according to the determinedtransmit order and transmits.

According to yet another embodiment of the present invention, a mobilestation apparatus comprises a number of receive antennas notifyingsignal transmit section that transmits a number of receive antennasnotifying signal indicating the number of receive antennas provided forthe mobile station apparatus.

According to still another embodiment of the present invention, ascheduling method comprises the steps of acquiring the numbers ofreceive antennas of communication partner stations; determining order inwhich data are transmitted based on the acquired numbers of the receiveantennas; and assigning the data to a plurality of transmit antennasaccording to the determined transmit order and transmitting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing an example of the configuration of a radiocommunication system according to embodiment 1 of the present invention;

FIG. 2 is a block diagram showing the internal configuration of a basestation apparatus according to embodiment 1;

FIG. 3 is a block diagram showing the internal configuration of a mobilestation apparatus according to embodiment 1;

FIG. 4 is a block diagram showing the internal configuration of othermobile station apparatus according to embodiment 1;

FIG. 5 is a view showing an example of the assignment of data totransmit antennas according to embodiment 1;

FIG. 6 is a block diagram showing the internal configuration of a basestation apparatus according to embodiment 2 of the present invention;

FIG. 7 is a block diagram showing the internal configuration of a mobilestation apparatus according to embodiment 2;

FIG. 8 is a block diagram showing the internal configuration of othermobile station apparatus according to embodiment 2;

FIG. 9 is a view showing an example of the assignment of data totransmit antennas according to embodiment 2;

FIG. 10 is a block diagram showing the internal configuration of a basestation apparatus according to embodiment 3 of the present invention;

FIG. 11 is a block diagram showing the internal configuration of amobile station apparatus according to embodiment 3;

FIG. 12 is a block diagram showing the internal configuration of othermobile station apparatus according to embodiment 3; and

FIG. 13 is a view showing an example of the assignment of data totransmit antennas according to embodiment 3.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

EMBODIMENT 1

FIG. 1 is a view showing an example of the configuration of a radiocommunication system according to embodiment 1 of the present invention.The radio communication system shown in FIG. 1 comprises a base stationapparatus 10 provided with two transmit antennas, a mobile stationapparatus 20 provided with one receive antenna, a mobile stationapparatus 30 provided with two receive antennas, and a mobile stationapparatus 40 provided with two receive antennas.

It is assumed that the base station apparatus 10 communicates with themobile station apparatuses 20, 30, and 40.

FIG. 2 is a block diagram showing the internal configuration of the basestation apparatus 10 according to embodiment 1. The base stationapparatus 10 shown in FIG. 2 comprises a transmit order determiningsection consisting of a buffer 102 and a scheduler 104, an encodingsection 106, a S/P (Serial/Parallel) converter 108, modulators 110-1 to110-2, spreading sections 112-1 to 112-2, radio transmitters 114-1 to114-2, transmit antennas 116-1 to 116-2, an antenna 118, a radioreceiver 120, a number of receive antennas notifying signal decoder 122,a transmit antennas assignment signal generator 124, and a radiotransmitter 126. Note that in the description below, the flow of datafrom the modulator 110-1 to the transmit antennas 116-1 and the flow ofdata from the modulator 110-2 to the transmit antennas 116-2 are eachcalled “sub-stream”.

The buffer 102, according to the scheduling by the scheduler 104, sendsout transmission data to the mobile station apparatus 20, 30, or 40. Thescheduler 104 performs scheduling to determine a data transmit order,depending on the numbers of the receive antennas of the respectivemobile station apparatuses based on respective number of receiveantennas notifying signals decoded by the number of receive antennasnotifying signal decoder 122. Here, the number of receive antennasnotifying signals are signals that are transmitted from the mobilestation apparatuses 20, 30, 40 and each notify the number of the receiveantennas of the respective mobile station apparatus.

Furthermore, the scheduler 104 notifies the transmit antennas assignmentsignal generator 124 of which transmit antenna is assigned which mobilestation apparatus's sub-stream as the scheduling result. The schedulingby the scheduler 104 will be described later.

The encoding section 106 encodes data sent out from the buffer 102 intoerror-correction coded data. The S/P converter 108serial/parallel-converts the error-correction coded data into twosub-streams. The modulators 110-1 and 110-2 modulate the sub-streamsrespectively. The spreading sections 112-1 and 112-2 spread thesub-streams respectively with the same spreading code. The radiotransmitters 114-1 and 114-2 perform predetermined radio processing (D/Aconversion, up convert, etc.) on the respective sub-streams, andtransmit at the same frequency and at the same time via thecorresponding transmit antennas 116-1 and 116-2 respectively.

The antenna 118 receives the number of receive antennas notifyingsignals transmitted from the mobile station apparatuses 20, 30, and 40and transmits a transmit antennas assignment signal generated by thetransmit antennas assignment signal generator 124. The radio receiver120 performs predetermined radio processing (down convert, A/Dconversion, etc.) on the number of receive antennas notifying signalsreceived. The number of receive antennas notifying signal decoder 122decodes the number of receive antennas notifying signals and notifiesthe numbers of the receive antennas of the mobile station apparatuses20, 30, and 40 to the scheduler 104. The transmit antennas assignmentsignal generator 124 generates the transmit antennas assignment signalindicating which transmit antenna is assigned which mobile stationapparatus's sub-stream. The radio transmitter 126 performs predeterminedradio processing (D/A conversion, up convert, etc.) on the transmitantennas assignment signal.

FIG. 3 is a block diagram showing the internal configuration of themobile station apparatus 20 according to embodiment 1. The mobilestation apparatus 20 shown in FIG. 3 comprises a receive antenna 202, aradio receiver 204, a despreading section 206, a demodulating/decodingsection 208, a number of receive antennas notifying signal generator210, a radio transmitter 212, an antenna 214, a radio receiver 216, anda transmit antennas assignment signal decoder 218.

The radio receiver 204 receives the signals of the sub-streamstransmitted from the base station apparatus 10 via the receive antenna202 and performs predetermined radio processing (down convert, A/Dconversion, etc.). The despreading section 206 despreads the receivedsignals. The demodulating/decoding section 208 demodulates and decodes asub-stream addressed to its own apparatus from among the sub-streamstransmitted from the base station apparatus 10 to obtain reception data.

The number of receive antennas notifying signal generator 210 generatesa number of receive antennas notifying signal for notifying the numberof the receive antennas (here, one) provided for its own apparatus tothe base station apparatus 10. The radio transmitter 212 performspredetermined radio processing (D/A conversion, up convert, etc.) on thenumber of receive antennas notifying signal and transmits via theantenna 214.

The antenna 214 receives the transmit antennas assignment signaltransmitted from the base station apparatus 10 and transmits the numberof receive antennas notifying signal generated by the number of receiveantennas notifying signal generator 210. The radio receiver 216 performspredetermined radio processing (down convert, A/D conversion, etc.) onthe transmit antennas assignment signal received via the antenna 214.The transmit antennas assignment signal decoder 218 decodes the transmitantennas assignment signal and notifies information indicating whichtransmit antenna of the base station apparatus 10 is assigned whichmobile station apparatus's sub-stream to the demodulating/decodingsection 208.

FIG. 4 is a block diagram showing the internal configuration of themobile station apparatus 30 according to embodiment 1. Note that themobile station apparatus 40 has the same configuration as the mobilestation apparatus 30. The mobile station apparatus 30 shown in FIG. 4comprises receive antennas 302-1 to 302-2, radio receivers 304-1 to304-2, despreading sections 306-1 to 306-2, a sub-stream separatingsection 308, a P/S converter 310, a demodulating/decoding section 312, achannel estimating section 314, a number of receive antennas notifyingsignal generator 316, a radio transmitter 318, an antenna 320, a radioreceiver 322, and a transmit antennas assignment signal decoder 324.

The radio receivers 304-1 and 304-2 receive the signals of thesub-streams transmitted from the base station apparatus 10 via thereceive antennas 302-1 and 302-2 respectively and perform predeterminedradio processing (down convert, A/D conversion, etc.). The despreadingsections 306-1 and 306-2 despread the received signals. The sub-streamseparating section 308 separates the despread received signals into therespective data of the sub-streams from the base station apparatus 10based on a channel estimating result. The P/S converter 310parallel/serial-converts the respective data of the two sub-streamsobtained by the separation into a series of data. Thedemodulating/decoding section 312 demodulates and decodes datacorresponding to a sub-stream transmitted to its own apparatus from thebase station apparatus 10 out of the series of data to obtain receptiondata. The channel estimating section 314 performs channel estimation onthe signals received by each of the receive antennas 302-1 and 302-2.

The number of receive antennas notifying signal generator 316 generatesa number of receive antennas notifying signal for notifying the numberof the receive antennas (here, two) provided for its own apparatus tothe base station apparatus 10. The radio transmitter 318 performspredetermined radio processing (D/A conversion, up convert, etc.) on thenumber of receive antennas notifying signal and transmits via theantenna 320.

The antenna 320 receives the transmit antennas assignment signaltransmitted from the base station apparatus 10 and transmits the numberof receive antennas notifying signal generated by the number of receiveantennas notifying signal generator 316. The radio receiver 322 performspredetermined radio processing (down convert, A/D conversion, etc.) onthe transmit antennas assignment signal received via the antenna 320.The transmit antennas assignment signal decoder 324 decodes the transmitantennas assignment signal radio-processed and notifies informationindicating which transmit antenna of the base station apparatus 10 isassigned which mobile station apparatus's sub-stream to thedemodulating/decoding section 312.

Next, in the radio communication system including the base stationapparatus 10 and the mobile station apparatuses 20, 30 and 40 configuredas above, the scheduling operation will be described.

First, the number of receive antennas notifying signals generated by thenumber of receive antennas notifying signal generators 210 and 316 ofthe mobile station apparatuses 20, 30 and 40 are transmitted from therespective mobile station apparatuses. The number of receive antennasnotifying signals are received by the antenna 118 of the base stationapparatus 10. Then, the radio receiver 120 performs predetermined radioprocessing (down convert, A/D conversion, etc.), and the number ofreceive antennas notifying signal decoder 122 decodes the number ofreceive antennas notifying signals and notifies the number of thereceive antennas of each mobile station apparatus to the scheduler 104.

Then, the scheduler 104 performs a scheduling as follows: whentransmitting data to the mobile station apparatus 20 the number of whosereceive-antennas is one, both of the two transmit antennas 116-1 and116-2 are assigned the same data addressed to the mobile stationapparatus 20, and when transmitting data to the mobile stationapparatuses 30 and 40 the number of whose receive antennas is two, thetwo transmit antennas 116-1 and 116-2 are assigned respective differentdata sets (that is, two different data sets addressed to the mobilestation apparatus 30, two different data sets addressed to the mobilestation apparatus 40, or respective data sets addressed to the mobilestation apparatuses 30 and 40).

Specifically, let the mobile station apparatuses 20, 30, and 40 be userA, user B, and user C respectively. As shown in FIG. 5 for example, thescheduler 104 performs scheduling such that at t1 the two transmitantennas 116-1 and 116-2 are assigned data A1 addressed to user A, at t2the transmit antennas 116-1 and 116-2 are assigned respectively data B1addressed to user B and data C1 addressed to user C, and at t3 and t4they are assigned like at t1 and t2 respectively.

Note that data A1 and A2 being assigned to the two transmit antennas116-1 and 116-2 at t1 and t3 can be realized by the scheduler 104controlling the buffer 102 to make a copy of data A1 or A2 and outputthe data and its copy successively and then by the S/P converter 108parallel/serial-converting.

Moreover, in the present embodiment a description has been made takingas an example the case where the number of the transmit antennas of thebase station apparatus 10 is two, the number of the receive antennas ofthe mobile station apparatus 20 is one, and the numbers of the receiveantennas of the mobile station apparatuses 30 and 40 are two, but thesenumbers of antennas can be any number. Since the mobile stationapparatus can separate the same number of sub-streams as the receiveantennas provided thereto, when the base station apparatus has Ntransmit antennas (that is, can transmit N sub-streams), the schedulingneed only be performed such that the same number of different data asthe receive antennas of a mobile station apparatus, having the smallestnumber of receive antennas, from among the mobile station apparatuses aspartners to which to transmit data at the same time are assigned torespective ones of the N transmit antennas.

For example, in the case where the base station apparatus has threetransmit antennas (can transmit three sub-streams), if one of the mobilestation apparatuses as partners to which to transmit data at the sametime has two receive antennas, the scheduling is performed such that twodifferent sub-streams are assigned to two of the three transmitantennas, or the two different sub-streams and a copy of one of them areassigned to the three transmit antennas. If all the mobile stationapparatuses as partners to which the base station apparatus transmitsdata at the same time have three or more receive antennas, thescheduling is performed such that three different sub-streams areassigned to the three transmit antennas.

The scheduler 104 notifies information about which transmit antenna isassigned which mobile station apparatus's sub-stream as the schedulingresult of the scheduler 104 to the transmit antennas assignment signalgenerator 124. The transmit antennas assignment signal generator 124generates a transmit antennas assignment signal for notifying theinformation about the assignment of the transmit antennas to each mobilestation apparatus. The radio transmitter 126 transmits the transmitantennas assignment signal via the antenna 118.

Meanwhile, the scheduler 104 controls the buffer 102, and the encodingsection 106 encodes data sent out from the buffer 102 intoerror-correction coded data. The S/P converter 108serial/parallel-converts the error-correction coded data into twosub-streams. Then, the modulators 110-1 and 110-2 modulate thesub-streams respectively; the spreading sections 112-1 and 112-2 spreadthe sub-streams with the same spreading code, and the radio transmitters114-1 and 114-2 transmit at the same frequency via the transmit antennas116-1 and 116-2 respectively.

Each mobile station apparatus receives the signals including asub-stream addressed thereto via the receive antenna 202, 302-1 or302-2. At the same time, each mobile station apparatus receives thetransmit antennas assignment signal via the antenna 214 or 320.

Then, the transmit antennas assignment signal decoder 218 or 324 decodesthe transmit antennas assignment signal and notifies information aboutthe assignment of the sub-streams to the transmit antennas in the basestation apparatus 10 to the demodulating/decoding section 208 or 312.

For the mobile station apparatus 20, because of receiving signalstransmitted with the same sub-stream assigned to the two transmitantennas, the contents of the transmit antennas assignment signalindicates that the two transmit antenna are both assigned the samesub-stream addressed to the mobile station apparatus 20. Meanwhile, forthe mobile station apparatuses 30 and 40, only a sub-stream addressedthereto being not necessarily assigned to the two transmit antennas, thecontents of the transmit antennas assignment signal indicates whichmobile station apparatus's sub-stream out of the two is assigned to eachof the first and second transmit antennas.

Based on the contents of the transmit antennas assignment signal, in themobile station apparatus 20 the demodulating/decoding section 208demodulates and decodes the sub-stream addressed thereto to obtainreception data. Meanwhile, in the mobile station apparatuses 30 and 40,the sub-stream separating section 308 separates the received signalsinto the respective data of the sub-streams from the base stationapparatus 10, and then the demodulating/decoding section 312 demodulatesand decodes the sub-stream addressed thereto to obtain reception data.

As described above, according to the present embodiment, the mobilestation apparatus notifies the number of its own receive antennas to thebase station apparatus, and when assigning data to a plurality oftransmit antennas, the base station apparatus performs scheduling suchthat the same number of different data as the receive antennas of amobile station apparatus having the smallest number of receive antennasare transmitted at the same time. Thus, even when a base stationapparatus transmits data to different mobile station apparatuses via aplurality of transmit antennas, all the mobile station apparatuses canprecisely receive data addressed thereto.

EMBODIMENT 2

The feature of embodiment 2 of the present invention is that each mobilestation apparatus reports an index indicating the quality of a channel(CQI: Channel Quality Indicator) to a base station apparatus, and thebase station apparatus performs scheduling based on the CQIs and thenumbers of receive antennas of the mobile station apparatuses. The radiocommunication system according to the present embodiment has the sameconfiguration as the radio communication system shown in FIG. 1, thusomitting a description thereof.

FIG. 6 is a block diagram showing the internal configuration of the basestation apparatus according to embodiment 2. The same parts as in thebase station apparatus 10 shown in FIG. 2 are indicated by the samereference numerals, and a description thereof is omitted.

The scheduler 104 a performs scheduling that determines a data transmitorder, depending on the numbers of receive antennas of the respectivemobile station apparatuses and CQIs between antennas based on respectivenumber of receive antennas notifying signals decoded by the number ofreceive antennas notifying signal decoder 122 and the CQIs decoded by aCQI decoder 402. The CQI decoder 402 decodes the CQIs transmitted by themobile station apparatuses. Here, the CQI is an index indicating thequality of a channel between one of the transmit antenna 116-1 and 116-2and a receive antenna of a mobile station apparatus, and, for example,CIR (Carrier to Interference Ratio) is used as the CQI.

FIG. 7 is a block diagram showing the internal configuration of a mobilestation apparatus according to embodiment 2. The mobile stationapparatus of FIG. 7 has one receive antenna, and the same parts as inthe mobile station apparatus 20 shown in FIG. 3 are indicated by thesame reference numerals, and a description thereof is omitted.

The channel estimating section 502 performs channel estimation on thesignals received by the receive antenna 202. A CQI measuring section 504measures CQIs between the transmit antenna 116-1 and 116-2 of the basestation apparatus and a receive antenna 202 of its own apparatus basedon the channel estimation result.

FIG. 8 is a block diagram showing the internal configuration of othermobile station apparatuses according to embodiment 2. The mobile stationapparatus of FIG. 8 has two receive antenna, and the same parts as inthe mobile station apparatus 30 shown in FIG. 4 are indicated by thesame reference numerals, and a description thereof is omitted.

A CQI measuring section 602 measures CQIs between the transmit antenna116-1 and 116-2 of the base station apparatus and receive antennas 302-1and 302-2 of its own apparatus based on the channel estimation result.

Next, in the radio communication system including the base stationapparatus and the mobile station apparatuses configured as above, thescheduling operation will be described.

Also in the present embodiment, first, each mobile station apparatusgenerates and transmits a number of receive antennas notifying signal tothe base station apparatus. At this time, each of the CQI measuringsections 504 and 602 measures CQI for each sub-stream transmitted fromthe transmit antenna 116-1 and 116-2 of the base station apparatus basedon the channel estimation result of the respective channel estimatingsection 502 or 314, and transmits the measured CQIs and the number ofreceive antennas notifying signal at the same time.

The CQIs and the number of receive antennas notifying signals arereceived by the antenna 118 of the base station apparatus. Then, theradio receiver 120 performs predetermined radio processing (downconvert, A/D conversion, etc.); the number of receive antennas notifyingsignal decoder 122 decodes the number of receive antennas notifyingsignals; the CQI decoder 402 decodes the CQIs; and they notify thenumber of the receive antennas of each mobile station apparatus and theCQI for each sub-stream to the scheduler 104 a.

Then, the scheduler 104 a performs scheduling as follows: whentransmitting data to the mobile station apparatus the number of whosereceive antennas is one, both of the two transmit antennas 116-1 and116-2 are assigned the same data addressed to the mobile stationapparatus, and when transmitting data to the mobile station apparatusesthe number of whose receive antennas is two, the two transmit antennas116-1 and 116-2 are assigned the respective different data sets.Furthermore, data is scheduled to be transmitted on a channel good inquality to each mobile station apparatus based on the CQIs notified bythe mobile station apparatus.

Specifically, let the mobile station apparatus having one receiveantenna be user A, and the mobile station apparatuses having two receiveantenna be user B, and user C. As shown in FIG. 9 for example, thescheduler performs scheduling such that at t1 the two transmit antennas116-1 and 116-2 are assigned data A1 addressed to user A, at t2 thetransmit antennas 116-1 and 116-2 are assigned respectively data B1 andB2 addressed to user B, and at t3 and t4 they are assigned like at t1and t2. Here, for example, at t3 it is detected from the CQIs that thechannel between the transmit antenna 116-1 and a receive antenna of userB and the channel between the transmit antenna 116-2 and a receiveantenna of user C are good in quality, and thus the scheduler 104 aperforms scheduling as shown in FIG. 9.

Note that data A1 being assigned to the two transmit antennas 116-1 and116-2 at t1 can be realized by the scheduler 104 a controlling thebuffer 102 to make a copy of data A1 and output the data and its copysuccessively and then by the S/P converter 108parallel/serial-converting.

Moreover, in the present embodiment a description has been made takingas an example the case where the number of the transmit antennas of thebase station apparatus is two, and the number of the receive antennas ofeach mobile station apparatuses is one or two, but these numbers ofantennas can be any number. Since the mobile station apparatus canseparate the same number of sub-streams as the receive antennas providedthereto, when the base station apparatus has N transmit antennas (thatis, can transmit N sub-streams), the scheduling need only be performedsuch that the same number of different data as the receive antennas of amobile station apparatus, having the smallest number of receiveantennas, from among the mobile station apparatuses as partners to whichto transmit data at the same time are assigned to respective ones of theN transmit antennas.

Then, as in embodiment 1, the scheduling result is transmitted as thetransmit-antennas-assignment signal via the antenna 118, and at the sametime data are transmitted respectively via the transmit antennas 116-1and 116-2 according to the scheduling. Then, each mobile stationapparatus demodulates and decodes data addressed thereto based on thetransmit antennas assignment signal to obtain reception data.

As described above, according to the present embodiment, each mobilestation apparatus reports CQI for each sub-stream to the base stationapparatus, and the base station apparatus performs scheduling, dependingon the reported CQIs and the numbers of the receive antennas of therespective mobile station apparatuses. Thus, in each mobile stationapparatus, quality in receiving data can be improved and wastefulretransmission of data is prevented so that throughput can be improved.

Note that, in the present embodiment, the base station apparatus mayadaptively change modulation schemes and error-correction coding schemesby using CQI for each sub-stream reported by the mobile stationapparatus. In this case, in the base station apparatus shown in FIG. 6,an encoding section for each sub-stream may be provided after the S/Pconverter 108 so that the encoding and modulation sections for eachsub-stream adaptively perform error-correction coding and modulation.

EMBODIMENT 3

The feature of embodiment 3 of the present invention is that incommunications of an OFDM (Orthogonal Frequency Division Multiple)scheme or an MC-CDMA (Multi Carrier-Code Division Multiple Access)scheme, each mobile station apparatus notifies the number of receiveantennas thereof to a base station apparatus. The radio communicationsystem according to the present embodiment has the same configuration asthe radio communication system shown in FIG. 1, hence omitting adescription thereof.

FIG. 10 is a block diagram showing the internal configuration of thebase station apparatus according to embodiment 3. The same parts as inthe base station apparatus shown in FIG. 6 are indicated by the samereference numerals, and a description thereof is omitted.

The CQI decoder 402 decodes the CQIs transmitted by the mobile stationapparatuses. Modulators 702-1 to 702-4 modulate respective data ofsubcarriers obtained by serial/parallel-conversion. IFFT (Inverse FastFourier Transform) sections 704-1 to 704-2 each perform inverse fastFourier transform on data of two subcarriers as a unit. While in thepresent embodiment a description will be made assuming that onesub-stream includes data of two subcarriers, the number of subcarriersincluded in each sub-stream can be any.

FIG. 11 is a block diagram showing the internal configuration of amobile station apparatus according to embodiment 3. The mobile stationapparatus shown in FIG. 11 has one receive antenna, and the same partsas in the mobile station apparatus shown in FIG. 7 are indicated by thesame reference numerals, and a description thereof is omitted.

An FFT (Fast Fourier Transform) section 802 fast-Fourier-transforms thesignals received by the receive antenna 202.

FIG. 12 is a block diagram showing the internal configuration of othermobile station apparatuses according to embodiment 3. The mobile stationapparatus shown in FIG. 12 has two receive antenna, and the same partsas in the mobile station apparatus shown in FIG. 8 are indicated by thesame reference numerals, and a description thereof is omitted.

FFT sections 902-1 to 902-2 fast-Fourier-transforms the signals receivedby the receive antennas 302-1 to 302-2 respectively.

Next, in the radio communication system including the base stationapparatus and the mobile station apparatuses configured as above, thescheduling operation will be described.

Also in the present embodiment, first, the number of receive antennasnotifying signal is generated and transmitted from each mobile stationapparatus to the base station apparatus. At this time, each of the CQImeasuring sections 504 and 602 measures CQIs of respective sub-streamstransmitted from the transmit antenna 116-1 and 116-2 of the basestation apparatus based on channel estimation result of the channelestimating section 502 or 314, and the measure CQIs are transmitted atthe same time as the number of receive antennas notifying signal.

The number of receive antennas notifying signals and the CQIs arereceived by the antenna 118 of the base station apparatus. Then, theradio receiver 120 performs predetermined radio processing (downconvert, A/D conversion, etc.), and the number of receive antennasnotifying signal decoder 122 decodes the number of receive antennasnotifying signals and the CQI decoder 402 decodes the CQIs to notify thenumber of the receive antennas of each mobile station apparatus and theCQI of each sub-stream to the scheduler 104 a.

Then, the scheduler 104 a performs scheduling as follows: whentransmitting data to the mobile station apparatus the number of whosereceive antennas is one, both of the two transmit antennas 116-1 and116-2 are assigned the same data addressed to the mobile stationapparatus, and when transmitting data to the mobile station apparatusesthe number of whose receive-antennas is two, the two transmit antennas116-1 and 116-2 are assigned the respective different data sets.Furthermore, data is scheduled to be transmitted on a channel good inquality to each mobile station apparatus based on the CQIs notified bythe mobile station apparatus. Yet further, the scheduler 104 a performsscheduling as follows: when transmitting data to the mobile stationapparatus the number of whose receive antennas is one, the same data issuperimposed on subcarriers of the same frequency in the respectivesub-streams, and when transmitting data to the mobile stationapparatuses the number of whose receive antennas is two, different dataare respectively superimposed on subcarriers of the same frequency inthe respective sub-streams.

Specifically, let the mobile station apparatus having one receiveantenna be user A, and the mobile station apparatuses having two receiveantenna be user B, and user C. As shown in FIG. 13 for example, thescheduler performs scheduling as follows: at t1 the subcarriers offrequency f1 in the respective sub-streams transmitted from the twotransmit antennas 116-1 and 116-2 are assigned data A1 addressed to userA, and the subcarriers of frequency f2 are assigned data A2 addressed touser A; at t2 the subcarrier of frequency f1 in the sub-streamtransmitted from the transmit antenna 116-1 is assigned data B1addressed to user B, the subcarrier of frequency f2 is assigned data C1addressed to user C, the subcarrier of frequency f1 in the sub-streamtransmitted from the transmit antenna 116-2 is assigned data B2addressed to user B, the subcarrier of frequency f2 is assigned data B3addressed to user B; and at t3 and t4 they are assigned like at t1 andt2.

Note that data A1 and A2 being assigned to the two transmit antennas116-1 and 116-2 at t1 can be realized by the scheduler 104 a controllingthe buffer 102 to make copies of data A1 and A2 and output data A1, A2,A1 (copy), and A2 (copy) in that order and then by the S/P converter 108parallel/serial-converting.

Moreover, in the present embodiment a description has been made takingas an example the case where the number of the transmit antennas of thebase station apparatus is two, and the number of the receive antennas ofeach mobile station apparatuses is one or two, but these numbers ofantennas can be any number. Since the mobile station apparatus canseparate the same number of sub-streams as the receive antennas providedthereto, when the base station apparatus has N transmit antennas (thatis, can transmit N sub-streams), the scheduling need only be performedsuch that the same number of different data as the receive antennas of amobile station apparatus, having the smallest number of receiveantennas, from among the mobile station apparatuses as partners to whichto transmit data at the same time are assigned to respective ones of theN transmit antennas.

Then, as in embodiment 1, the scheduling result is transmitted as thetransmit antennas assignment signal via the antenna 118, and at the sametime data are transmitted respectively via the transmit antennas 116-1and 116-2 according to the scheduling. Then, each mobile stationapparatus fast-Fourier-transforms the received signals, and demodulatesand decodes data addressed thereto based on the transmit antennasassignment signal to obtain reception data.

As described above, according to the present embodiment, incommunications using the OFDM scheme or the MC-CDMA scheme, even in thecase where a base station apparatus transmits data to different mobilestation apparatuses respectively via a plurality of transmit antennas,all the mobile station apparatuses can precisely receive data addressedthereto.

As described above, according to the present invention, in the casewhere data are transmitted to different receive apparatuses respectivelyvia a plurality of transmit antennas, all the receive apparatuses canprecisely receive data addressed thereto.

The present description is based on Japanese Patent Application No.2002-179818 filed on Jun. 20, 2002, which is herein incorporated byreference.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a radio communication system anda scheduling method.

1. A radio communication system that has a mobile station apparatus group of which at least one mobile station apparatus is provided with a plurality of receive antennas and a base station apparatus that transmits data to said mobile station apparatus group via a plurality of transmit antennas, wherein: each mobile station apparatus of said mobile station apparatus group comprises: a number of receive antennas notifying signal transmit section that transmits a number of receive antennas notifying signal indicating the number of receive antennas provided for the mobile station apparatus; and said base station apparatus comprises: a number of receive antennas notifying signal receive section that receives said number of receive antennas notifying signals; a transmit order determining section that determines order in which data are transmitted based on said number of receive antennas notifying signals received; and a data transmit section that assigns the data to said plurality of transmit antennas according to the determined transmit order and transmits.
 2. The radio communication system according to claim 1, wherein said base station apparatus further comprises: a transmit antennas assignment signal transmit section that transmits a transmit antennas assignment signal for notifying assignment of data to said plurality of transmit antennas, which assignment is set by said data transmit section.
 3. The radio communication system according to claim 1, wherein said transmit order determining section determines a transmit order so as to transmit the same number of different data as the receive antennas of a mobile station apparatus, having the smallest number of receive antennas, from among mobile station apparatuses as partners to which to transmit data simultaneously via said plurality of transmit antennas.
 4. The radio communication system according to claim 1, wherein: each mobile station apparatus of said mobile station apparatus group further comprises: a link quality measuring section that measures link qualities between the plurality of transmit antennas of said base station apparatus and receive antennas of the mobile station apparatus; and a link quality information transmit section that transmits information about the measured link qualities; and said base station apparatus further comprises: a link quality information receive section that receives the link quality information, wherein said transmit order determining section determines order in which data are transmitted based on the link quality information and the number of receive antennas notifying signals received.
 5. A base station apparatus that transmits data via a plurality of transmit antennas, comprising: a number of receive antennas notifying signal receive section that receives number of receive antennas notifying signals indicating the numbers of receive antennas provided for communication partner stations; a transmit order determining section that determines order in which data are transmitted based on said number of receive antennas notifying signals received; and a data transmit section that assigns the data to said plurality of transmit antennas according to the determined transmit order and transmits.
 6. The base station apparatus according to claim 5, further comprising: a transmit antennas assignment signal transmit section that transmits a transmit antennas assignment signal for notifying assignment of data to said plurality of transmit antennas, which assignment is set by said data transmit section.
 7. The base station apparatus according to claim 5, wherein said transmit order determining section determines a transmit order so as to transmit the same number of different data as the receive antennas of a communication partner station, having the smallest number of receive antennas, from among communication partner stations to which to transmit data simultaneously via said plurality of transmit antennas.
 8. The base station apparatus according to claim 5, further comprising: a link quality information receive section that receives link quality information indicating link qualities between said plurality of transmit antennas and receive antennas of communication partner stations, wherein said transmit order determining section determines order in which data are transmitted based on the link quality information and the number of receive antennas notifying signals received.
 9. The base station apparatus according to claim 8, wherein said data transmit section changes modulation schemes and encoding schemes for data assigned to said plurality of transmit antennas, adaptively depending on said link quality information and transmits.
 10. The base station apparatus according to claim 5, wherein said data transmit section superimposes data assigned respectively to said plurality of antennas on a plurality of carriers and transmits.
 11. A mobile station apparatus that communicates with the base station apparatus according to claim 5, the mobile station apparatus comprising: a number of receive antennas notifying signal transmit section that transmits a number of receive antennas notifying signal indicating the number of receive antennas provided for the mobile station apparatus to said base station apparatus.
 12. A scheduling method comprising the steps of: acquiring the numbers of receive antennas of communication partner stations; determining order in which data are transmitted based on the acquired numbers of the receive antennas; and assigning the data to a plurality of transmit antennas according to the determined transmit order and transmitting. 